Currently two primary methods of roadbed preparation are employed: 1) excavating the moist or wet roadbed and mixing lime thoroughly with the soil to allow the exothermic reaction between the lime and water to release sufficient heat to dry the soil and 2) use a process employing jet engine exhaust to directly heat the roadbed from the top down. Both processes are labor intensive and have very high initial capital equipment and operating costs. In addition, lime dust can cause serious skin burns to operating personnel. Further, both processes require days for drying a mile of typical roadbed, while the microwave apparatus described in this invention will provide a dry roadbed, suitable for paving, usually within one day. One can readily see the impact in re-drying efforts expended in time, fuel and/or lime necessary after a rainstorm. It should also therefore be apparent that utilization of this invention returns the wet roadbed to a surface suitable for paving in less time. As this invention only requires one person for operation, combined with less fuel consumption and without lime addition, operating costs are substantially less.
It has been estimated that a typical jet engine-based system is labor-intensive at a cost of approximately $100,000/mile. Lime mixing operations are also labor-intensive at a cost of approximately $84,000/mile. Both operations take about 7-10 days per mile.
Weather obvious plays a critical role in preparation and installation of roadbeds throughout the typical 6-8 month season. Road construction delays due to inclement weather, results in escalating costs. Many efforts to substantially improve efficiency or reduce costs have failed to meet their objectives either from an economic or technical point of view. Microwaves have been used to reheat and dry various materials, due to the excitation of the water molecules contained within the sample. Heating typically occurs from the inside out. Convection heating has also been used to reheat and dry various materials, and heating typically occurs from the outside in. It is well known that hot air is capable of holding more moisture than cold air. The combined effect of applying microwave energy and hot recirculating air is the most effective method of drying. This invention will improve roadbed drying efficiency and extend the roadbed construction operation to typically 10-11 months.
Therefore, what is needed is a microwave-based continuous drying process without any pretreatment of the roadbed which only needs one operator/driver with a completion of one mile of roadbed preparation in about four hours time.
There is also a need for support in the field of agriculture as a replacement for the traditional approach of burning the remaining “stubble” which is seen in the fields post-harvesting. By the surface application of microwaves, this stubble can be reduced to a fragile ash which can more easily be plowed back into the soil without any negative impact on the desirable nitrogen and phosphorus.